The conventional methods of controlling distribution of light of a lamp are to redirect or control flux of a light source with a reflector or a lens, or to cut a part of flux with an absorption body in order to eliminate the light which goes to outside of the desired area. However, the elimination of a part of the flux of a lamp for such an improvement has resulted in a low energy efficiency. Many of the conventional lighting devices for uniform radiation through the panels of such lighting devices have a plurality of fluorescent lamps behind each of the translucent diffusion panels and radiate the flux of lamps out through each of the diffusion panels.
Such devices have failed to have sufficiently uniform light intensity throughout the radiation panel due to cause of light and dark bands on the surface of the radiation panel along the arrangement of the fluorescent lamps. Elimination of such light and dark bands by arranging the lamps closer to one another or by using a high diffusion panel of conventional translucent material for the radiation panel decreases the energy efficiency.
It is an objective of the present invention to provide a lighting device in a distribution control type which forwards much greater amount of the flux from a lamp (lamps) into a specified range of light distribution and much less amount of the flux to the outside of the range than any conventional device does, i.e. a lighting device in a distribution control type which provides a desired light distribution with a high energy efficiency.
It is further objective of the present invention to provide a lighting device in a radiation panel type with no cause of light and dark bands on the radiation panel, i.e. uniform radiation throughout the panel with a high energy efficiency in exploitation of the above light distribution control technology.